Nastapoka arc

[1] While the circular shape has led to suggestions that it represents an impact crater, there is no evidence for this hypothesis, and it is thought to have been formed as a result of lithospheric flexure during the Trans-Hudson orogeny.

[3] A large triangular area surrounding Richmond Gulf, which includes a short segment of the Nastapoka arc, is underlain by about 1 kilometer (0.62 mi) of undeformed, pink and red, mainly fluvial, feldspar-rich sandstone that is interbedded with minor beds of conglomerate and basaltic, subaerial lava flows.

Adjacent to the Nastapoka arc, these strata form a homocline that dips gently westward and consists of unmetamorphosed to slightly metamorphosed sandstone, stromatolite-bearing dolomite, banded iron formation, and basalt.

In the same volume, Wilson[7] evaluates Beals's interpretation and proposes an alternative hypothesis that the Nastapoka arc formed as the result of a continental-scale collision of pre-existing Archean continents and closure of an ancient ocean basin.

In August 1972, Robert S. Dietz and J. Paul Barringer[8] conducted an extensive search of much of the Nastapoka arc with First Nations and Inuit canoes and fishing boats in an investigation of its impact origin.

general consensus is that it is an arcuate boundary of tectonic origin between the Belcher Fold Belt and crystalline rocks of the Superior craton created during the Trans-Hudson orogeny about 2.0–1.8 billion years ago.